TODO:
- Rename Guarded to Bounded?
- Consider bounded array (where size and indexes are bounded quantities).
- Implement non-CAPNP_DEBUG_TYPES fallback.
  - Don't allow casting kj::maxValue to bounded type, this won't work right when not using debug types!
- Verify that this change doesn't hurt performance.

This method provides kj-ish interface to parse numbers.

Moves code from capnp json decoder to kj::StringPtr.

Fix JSON handler for DynamicStruct. The handler needs to be told the struct's schema to construct an orphan.

Also improve error message when addTypeHandler() is given a handler for a dynamic type but no specific schema is specified. We could support this eventually but we don't presently.

Problem discovered and initial test case contributed by Harris Hancock.

json.capnp.{h,c++} must have been generated using an earlier version of
the code generator, or an earlier version of capnpc-c++.

Cloning capnproto/master, building and installing, then running
regenerate-bootstraps.sh results in this diff.

This allows to preserve these values in capnp -> json -> capnp conversion.

This encapsulates the input array, hiding it from the parser's methods.
Access is forced to go through `advance` and `consume*` methods on the
new `Input` object. The aim is to make it harder to have errors like
https://github.com/sandstorm-io/capnproto/pull/270

This reduces dependencies on stdc++. For rationale, see
  https://github.com/kamalmarhubi/capnproto/commit/62a562f6d2c7bd147958106a1cf4169533d43f83#commitcomment-14375773

Such values are not allowed by the JSON spec. We match the behavior of
JSON.stringify in Firefox and Chrome.

fixes https://github.com/sandstorm-io/capnproto/issues/261

Per spec.